1. Field of the Invention
The present invention is concerned with a resistor composition for a spark plug having a resistor sealed therein.
2. Description of the Prior Art
It is well known that a spark plug having a resistance value of 0.5 to 20 K.OMEGA. sealed in an electrode bore of a porcelain insulator of the spark plug which comprises placing an electrically conductive glass between a center electrode and a terminal electrode, both electrodes being placed face-to-face with respect to each other in the electrode bore, prevents noise as well as the generation of an interfering electric wave upon sparking.
These resistors are generally produced from a resistor composition comprising a glass, which is necessary for sealing, containing carbon or metal oxides, metal carbides and metals, etc. as an electrically conductive material, and, as necessary, inorganic fillers such as alumina, zircon, zirconia, silica, mullite, and clays, etc.
After various investigations on glasses, electrically conductive materials and inorganic fillers which are used to produce these resistors and on the influences thereof upon efficiency, the present invention has been achieved, particularly using inorganic fillers which have not been used heretofore.